1. Field of the Disclosure
The invention generally relates to a method for forming a fine pattern of a semiconductor device.
2. Brief Description of Related Technology
Due to the popularization of information media such as computers, semiconductor device technology has advanced rapidly. Semiconductor devices are required to operate at a high speed and to have a high storage capacity. Hence, it is desirable to manufacture high-capacity semiconductor memory devices with improved integration, reliability, and characteristics for accessing data.
To improve device integration, photolithography technology has developed to form fine patterns. The photolithography technology includes an exposure technology using chemically amplified Deep Ultra Violet (DUV) light sources such as ArF (193 nm) and VUV (157 nm), and a technology for developing photoresist materials suitable for the exposure light sources.
As semiconductor devices become smaller, it is important to control a critical dimension of a pattern line-width in the photolithography technology. Generally, the processing speed of semiconductor devices depends on the critical dimension of the pattern line-width. For example, as the line-width of the pattern is decreased, the processing speed is increased to improve device performance.
To improve resolution of photolithography technology and extend a process margin, a double patterning technology has been developed. The double patterning technology includes processes whereby a photoresist-coated wafer is respectively exposed by two masks, and then developed, thereby obtaining a complicated pattern, a dense pattern, or an isolated pattern.
Because the double patterning technology uses two masks for patterning, the manufacturing cost are greater than those of a single patterning technology using a single mask. And, since the technology requires much time to manufacture semiconductor device, the throughput is low. Moreover, it is difficult to control an overlay degree of patterns. As a result, when a pattern having a smaller pitch than a resolution limit of the exposer is formed in the cell region, illusory images overlap. Therefore, the double patterning technology does not obtain a desired pattern. In alignment, mis-alignment occurs by inaccuracy in overlay of patterns.